Slide surface construction

ABSTRACT

A slide surface construction is formed of an aggregate of metal crystals on a surface of a slide member. The area rate A of pyramid-shaped metal crystals in the slide surface is in the range of A≧40%, and the oxygen (O) content and/or the phosphorous (P) content in the aggregate is in a range of 0≧0.2% by weight and P≧0.04% by weight. The slide surface takes on an intricate aspect due to the presence of the large number of hexagonal pyramid-shaped metal crystals and hence, has a good oil retention. In addition, the wearing of the hexagonal pyramid-shaped metal crystals is inhibited by an increase in hardness caused by the oxygen contained, and therefore, the oil retention is maintained. Thus, the slide surface construction exhibits an excellent seizure resistance. In addition to oxygen (O) and/or phosphorous (P), the elements that may be added to the aggregate include hydrogen (H), carbon (C) and boron (B).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a slide surface construction, and particularly, to a slide surface construction formed of an aggregate of metal crystals and having a high hardness.

2. Description of the Related Art

Such conventionally known slide surface constructions include an Fe-plated layer, for example, which is provided on outer peripheral surfaces of a land portion and a skirt portion of a substrate made of a steel in a piston for an internal combustion engine for the purpose of providing an enhancement in wear resistance.

However, the known slide surface construction has a problem that under existing circumstances where speed and output of the internal combustion engine have tended to increase, the known slide surface construction is not sufficient in oil retaining property, namely, oil retention and is poor in seizure resistance due to a relatively smooth slide surface thereof.

Therefore, the present applicant has proposed a slide surface construction including a large number of pyramid-shaped metal crystals in a slide surface thereof (for example, see Japanese Patent Application Laid-open No.174089/94).

If the slide surface construction is formed in this manner, adjacent pyramid-shaped metal crystals assume mutually biting states and hence, the slide surface takes on an intricate aspect comprising a large number of fine crests, a large number of fine valleys formed between the crests, and a large number of fine swamps formed due to the mutual biting of the crests. Therefore, the slide surface construction has a good oil retention. Thus, the seizure resistance of the slide surface construction is enhanced.

However, as a result of various reviews of the slide surface construction, it has been made clear that the slide surface construction has a relatively low hardness and hence, in order to accommodate a more severe sliding environment, it is necessary to enhance the hardness of the slide surface construction to inhibit or resist the wearing of the pyramid-shaped metal crystals in such sliding environment, thereby allowing the slide surface construction to maintain a good oil retention.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a slide surface construction of the above-described type, which has a high hardness, whereby the wearing of the pyramid-shaped metal crystals can be inhibited in a severer sliding environment, thereby maintaining a good oil retention.

To achieve the above object, according to the present invention, there is provided a slide surface construction, which is formed of an aggregate of metal crystals, wherein the area rate A of pyramid-shaped metal crystals in a slide surface is in a range of A≧40%, and the aggregate contains at least one of oxygen (O) and phosphorus (P), the O content being in a range of O≧0.2% by weight, and the P content being in a range of P≧0.04% by weight.

If the area rate A of pyramid-shaped metal crystals is set in the above-described range, the adjacent pyramid-shaped metal crystals assume mutually biting states. Therefore, the slide surface takes on an intricate aspect comprising a large number of fine crests, a large number of fine valleys formed between the crests, and a large number of fine swamps formed due to the mutual biting of the crests.

If the content of O (oxygen) and/or P (phosphorus) in the aggregate is set in the above-described range, the hardness of the slide surface construction can be enhanced substantially.

In such a slide surface construction, the wearing of the pyramid-shaped metal crystals is inhibited or resisted, even if the slide surface construction is placed in a severe sliding environment. Therefore, under lubrication, the oil retention of the slide surface construction is maintained satisfactorily and under non-lubrication the dispersion of a sliding load is provided by the large number of fine pyramid-shaped metal crystals. Thus, the slide surface construction exhibits an excellent seizure resistance under both lubrication and non-lubrication.

If the area rate A of the pyramid-shaped metal crystals is lower than 40%, the slide surface tends to be simplified and hence, such area rate A lower than 40% is undesirable. If the O content is lower than 0.2% by weight and/or the P content is lower than 0.04% by weight, the degree of enhancement in hardness of the slide surface construction is lowered. On the other hand, it is desirable that the upper limit of the O content is equal to 22.9% by weight. If the O content is higher than 22.9% by weight, a wustite is liable to be produced. If the wustite is produced and segregated at a grain boundary, the strength of the slide surface construction is lowered.

It is desirable that the upper limit of the P content is equal to 11.5% by weight. If the P content is higher than 11.5% by weight, a metal phosphide, Fe₃ P is produced in an increased amount. For this reason, the metal crystals are liable to be granulated in the slide surface, and the strength of the slide surface construction is lowered due to the grain boundary segregation of Fe₃ P.

In addition, according to the present invention, there is provided a slide surface construction, which is formed of an aggregate of metal crystals, wherein the area rate A of pyramid-shaped metal crystals in a slide surface is in a range of A≧40%, and the aggregate contains at least one of oxygen (O) and phosphorus (P) and at least one of hydrogen (H) and carbon (C), the O content being in a range of O≧0.2% by weight, the P content being in a range of P≧0.04% by weight, the H content being in a range of H≧0.01% by weight, and the C content being in a range of C≧0.03% by weight.

If a particular amount of hydrogen (H) and/or a particular amount of carbon (C) are (is) contained in the slide surface construction along with oxygen (O) and phosphorus (P), the seizure resistance of the slide surface construction can be further enhanced. This is due to a reason which will be described below.

If the content of H in the aggregate is set in the above-described range, the hardness of the pyramid-shaped metal crystals can be enhanced, and at least some of the hydrogen (H) contained in the aggregate can be incorporated in the pyramid-shaped metal crystals.

When such slide surface construction is slid, the plastic deformation of tip ends of the pyramid-shaped metal crystals is avoided, and the tip ends of the pyramid-shaped metal crystals are sheared and worn in a direction intersecting a direction of the height due to a brittleness caused by the hydrogen (H) contained in the pyramid-shaped metal crystals. As a result, the oil retention by the valleys is insured, and the surface-on-surface sliding is permitted to occur, leading to a reduced friction coefficient. Thus, the slide surface construction exhibits an excellent sliding characteristic.

If the H content is lower than 0.01% by weight, the degree of enhancement in hardness of the pyramid-shaped metal crystals is lowered. In addition, the amount of H incorporated in the pyramid-shaped metal crystal is decreased and hence, the above-described shearing is not caused. On the other hand, it is desirable that the upper limit of the H content is equal to 0.1% by weight. If the H content is higher than 0.1% by weight, the hardness HmV of the slide surface construction is equal to or higher than 900 and for this reason, the slide surface construction is liable to be cracked.

If the content of C in the aggregate is set in the above-described range, the hardness of the slide surface construction can be enhanced substantially.

If the C content is lower than 0.03% by weight, the degree of enhancement in hardness of the slide surface construction is lowered. On the other hand, it is desirable that the upper limit of the C content is equal to 0.8% by weight. If the C content is higher than 0.8% by weight, it is difficult to form the metal crystals into the pyramid shape in the slide surface.

Further, according to the present invention, there is provided a slide surface construction, which is formed of an aggregate of metal crystals, wherein the aggregate has a large number of columnar metal crystals which are grown from a substrate and whose tip ends are formed of pyramid-shaped metal crystals, the area rate A of the pyramid-shaped metal crystals in a slide surface being in a range of A≧40%, and the aggregate contains boron (B), and at least one of oxygen (O) and phosphorus (P), or contains boron (B) and at least one of oxygen (O) and phosphorus (P) and at least one of hydrogen (H) and oxygen (O), the B content being in a range of B≧0.01% by weight, the O content being in a range of O≧0.2% by weight, the P content being in a range of P≧0.04% by weight, the H content being in a range of H≧0.01% by weight, and the C content being in a range of C≧0.03% by weight.

In the above feature of the present invention, the functions and effects of oxygen (O), phosphorus (P), hydrogen (H) and carbon (C) are as described above. The function and effect of boron (B) is as follows.

If a particular amount of B is contained in the aggregate, as described above, boron (B) is preferentially precipitated in a grain boundary between adjacent columnar metal crystals to reinforce the grain boundary. In addition, the diametrical growth of the adjacent columnar metal crystals is inhibited by the preferential precipitation of B in the grain boundary and hence, these columnar metal crystals are finely divided, resulting in an enhanced hardness of the slide surface construction. In this manner, the enhancement in hardness of the slide surface construction is achieved.

However, if the B content is lower than 0.01% by weight, the ability to reinforce the grain boundary and the ability to inhibit the diametrical growth are lowered and for this reason, it is impossible to enhance the hardness of the slide surface construction. It is desirable that the upper limit of the B content is equal to 3.7% by weight. If the B content is higher than 3.7% by weight, a B-based intermetallic compound is liable to be precipitated in the grain boundary. If such B-based intermetallic compound is precipitated, the resulting slide surface construction has a reduced strength.

The slide surface construction formed with the area rate A of the pyramid-shaped metal crystals, the added elements and the contents of these elements being specified, exhibits an excellent sliding characteristic in a severe sliding environment such as under a high surface pressure or the like.

The above and other objects, features and advantages of the invention will become apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a broken-away perspective view of an essential portion of a piston pin;

FIG. 2 is a perspective view of a body-centered cubic structure and its (hhh) plane and (2hhh) plane;

FIG. 3 is an enlarged sectional view taken along a line 3--3 in FIG. 1;

FIG. 4 is a view taken along an arrow 4 in FIG. 3;

FIG. 5 is a plan view of a trigonal pyramid-shaped metal crystal;

FIG. 6 is a diagrammatic illustration of a model of the trigonal pyramid-shaped metal crystal;

FIG. 7 is a diagrammatic illustration of the model for explaining the wearing of the pyramid-shaped metal crystal;

FIG. 8 is a diagrammatic illustration for explaining the inclination of an (hhh) plane in the body-centered cubic structure;

FIG. 9 is a waveform of an output from a power source for an electrolytic plating;

FIG. 10 is an X-ray diffraction pattern for an example 4;

FIG. 11A is a photomicrograph showing the crystal structure of a slide surface of the example 4;

FIG. 11B is a photomicrograph showing the crystal structure of a vertical section of the example 4;

FIG. 12 is a graph illustrating the relationship between the oxygen O content and the hardness;

FIG. 13 is a graph illustrating the relationship between the oxygen O content and the seizure generating load;

FIG. 14 is a graph illustrating the relationship between the area rate A of trigonal and hexagonal pyramid-shaped Fe crystals and the seizure generating load;

FIG. 15 is an X-ray diffraction pattern for another example 4;

FIG. 16 is a photomicrograph showing the crystal structure of the slide surface of the example 4 of FIG. 15;

FIG. 17 is a graph illustrating the relationship between the P content and the hardness;

FIG. 18 is a graph illustrating the relationship between the P content and the seizure generating load;

FIG. 19 is a graph illustrating the relationship between the area rate A of trigonal and hexagonal pyramid-shaped Fe crystals and the seizure generating load;

FIG. 20 is a graph illustrating a first example of the relationship between elements contained and the seizure generating load;

FIG. 21 is a photomicrograph showing the crystal structure of a vertical section of an example 1 after a sliding test;

FIG. 22 is a graph illustrating a second example of the relationship between elements contained and the seizure generating load;

FIG. 23 is a graph illustrating a third example of the relationship between elements contained and the seizure generating load;

FIG. 24 is a photomicrograph showing the crystal structure of the vertical section of another example 1;

FIG. 25 is a graph illustrating the relationship between the sputtering depth and the related density of B;

FIG. 26 is a graph illustrating a fourth example of the relationship between elements contained and the seizure generating load;

FIG. 27 is a graph illustrating a fifth example of the relationship between elements contained and the seizure generating load;

FIG. 28 is a graph illustrating a sixth example of the relationship between elements contained and the seizure generating load; and

FIG. 29 is a graph illustrating a seventh example of the relationship between elements contained and the seizure generating load.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a piston pin 1 for an internal combustion engine includes a pipe-like substrate 2 made of a steel. A lamellar slide surface construction 4 is formed on an outer peripheral surface 3 of the substrate 2 by plating.

The slide surface construction 4 is formed of an aggregate of metal crystals having a body-centered cubic structure (a bcc structure) as shown in FIG. 2 in the illustrated embodiment. The aggregate includes a large number of columnar metal crystals 5 which are grown from the substrate 2, as shown in FIG. 3. Each of the columnar metal crystals 5 is at least one of an (hhh) oriented metal crystal with its (hhh) plane (by Miller indices) oriented toward a slide surface 4a, or a (2hhh) oriented metal crystal with its (2hhh) planes (by Miller indices) oriented toward the slide surface 4a.

When the columnar metal crystal 5 is the (hhh) oriented metal crystal, tip ends of the columnar metal crystals 5 can be formed into hexagonal pyramid-shaped metal crystals 6 as shown in FIG. 4, or trigonal pyramid-shaped metal crystals 7 as shown in FIG. 5 in the slide surface 4a. The hexagonal pyramid-shaped metal crystals 6 are small in average grain size and substantially uniform in grain size, as compared with the trigonal pyramid-shaped metal crystals 7. In the hexagonal pyramid-shaped metal crystals 6 or the like, there is an interrelation between the grain size and the height and hence, the grain sizes are uniform, which indicates that the heights are substantially equal to one another.

When the columnar metal crystal 5 is the (2hhh) oriented metal crystal, tip ends of the columnar metal crystals 5 can be formed into small pyramid-shaped metal crystals.

The area rate A of the pyramid-shaped metal crystals such as hexagonal and trigonal pyramid-shaped metal crystals 6 and 7 and the small pyramid-shaped metal crystals is set in a range of A≧40% (including A≧100%).

If the area rate A is set in such range, for example, the hexagonal pyramid-shaped metal crystals 6 are formed into states with adjacent ones biting into each other, as shown in FIG. 4. Thus, the slide surface 4a has an enlarged surface area, as compared with a slide surface formed of trigonal pyramid-shaped metal crystals 7, and takes on a very intricate aspect comprising a large number of extremely fine crests 8, a large number of extremely fine valleys 9 formed between the crests 8, and a large number of extremely fine swamps 10 formed due to mutual biting of the crests 8.

The aggregate contains oxygen (O) and/or phosphorus (P). The O content is set in a range of O≧0.2% by weight, and the P content is set in a range of P≧0.04% by weight. If the O content and/or the P content are set in such range, the hardness of the slide surface construction can be enhanced substantially.

In such slide surface construction 4, the wearing of the hexagonal pyramid-shaped metal crystals can be inhibited even if the slide surface construction 4 is put under a severe sliding environment. Therefore, under lubrication the oil retention of the slide surface construction 4 is maintained and under non-lubrication the dispersion of a sliding load is provided by the infinite number of extremely fine hexagonal pyramid-shaped metal crystals 6. Thus, the slide surface construction 4 exhibits an excellent seizure resistance both under lubrication and under non-lubrication.

Further, as a result of uniform fine division of the hexagonal pyramid-shaped metal crystals 6, a local increase in surface pressure can be avoided, and the fine division of the sliding load can be achieved. Thus, the slide surface construction 4 exhibits an excellent wear resistance not only under lubrication but also under non-lubrication.

The aggregate may contain oxygen (O) and/or phosphorus (P), and hydrogen (H) and/or carbon (C) for purpose of providing a function and effect similar to those described above. In this case, the O content is in a range of O≧0.2% by weight; the P content is in a range of P≧0.04% by weight; the H content is in a range of O≧0.01% by weight; and the C content is in a range of O≧0.03% by weight.

Further, the aggregate may contain oxygen (O) and/or phosphorus (P), and boron (B), or may contain (O) and/or phosphorus (P), boron (B), and hydrogen (H) and/or carbon (C) for purpose of providing a function and effect similar to those described above. In this case, the O content is in a range of O≧2% by weight; the P content is in a range of ≧0.04% by weight; the B content is in a range of B≧0.01% by weight; the H content is in a range of O≧0.01% by weight; and the C content is in a range of O≧0.03% by weight.

If the H content in the aggregate is set in such range, the hardness of the hexagonal pyramid-shaped metal crystals 6 and the like can be enhanced, and at least some of the hydrogen (H) contained in the aggregate can be incorporated in the hexagonal pyramid-shaped metal crystals 6 and the like.

When such slide surface construction 4 is slid, the plastic deformation of tip ends of the hexagonal pyramid-shaped metal crystals 6 and the like can be avoided, and the tip ends of the hexagonal pyramid-shaped metal crystals 6 and the like are sheared and worn in a direction intersecting a direction of the height due to a brittleness caused by the incorporation of hydrogen in the hexagonal pyramid-shaped metal crystals 6 and the like. As a result, the oil retention by the valleys 9 is insured, and the surface-on-surface sliding is permitted to occur, leading to a reduced friction coefficient. Thus, the slide surface construction exhibits an excellent sliding characteristic.

One of the reasons why the shearing occurs is that a phenomenon which will be described below can be presumed from the photomicrograph showing the crystal structure of the vertical section of the slide surface construction after a sliding test. For example, it is believed that the hexagonal pyramid-shaped metal crystal 6 has a structure in which a large number of cubic lattices 11 are stacked one on another, as shown in FIG. 6, and at least some of the hydrogen exists on a crystal plane which is in a relation intersecting (at a right angle in the illustrated embodiment) the direction of the height within the hexagonal pyramid-shaped metal crystal 6, i.e., an (hhh) plane and hence, when the slide surface construction is slid, the tip ends of the hexagonal pyramid-shaped metal crystals 6 are sheared at a preselected (hhh) plane, as shown in FIG. 7. In this case, because the (hhh) plane is a crystal plane having a high surface energy, a smooth plane produced by the shearing has a good wettability to oil and hence, an oil film is immediately formed on the slide surface 4a after being worn.

If the C content in the aggregate is set in the above-described range, the hardness of the slide surface construction 4 can be enhanced substantially.

If the B content in the aggregate is set in the above-described range, boron is preferentially precipitated in a grain boundary 12 (see FIG. 3) between the adjacent columnar metal crystals 5 to reinforce the grain boundary 12. In addition, the diametrical growth of the adjacent columnar metal crystals 5 is inhibited by the preferential growth of the boron in the grain boundary 12. Therefore, the columnar metal crystals 5 are finely divided, resulting in an enhanced hardness of the slide surface construction. In this manner, the enhancement in hardness of the slide surface construction is achieved.

As shown in FIG. 8, the inclination of the (hhh) plane with respect to a phantom plane 13 along the slide surface 4a appears as an inclination of the hexagonal or trigonal pyramid-shaped metal crystal 6, 7 and hence, an influence is imparted to the oil retention and the wear resistance of the slide surface construction. The inclination angle θ formed by the (hhh) plane with respect to the phantom plane 13 is set in a range of 0°≧θ≧15°. In this case, the direction of inclination of the (hhh) plane is not limited. If the inclination angle θ is larger than 15°, the slide surface construction 4 has a reduced oil retention and a reduced wear resistance. The inclination angle θ also applies to the (2hhh) plane.

Examples of the metal crystal having the bcc structure include simple crystals of Fe, Cr, Mo, W, Ta, Zr, Nb, V and the like and crystals of alloys of these elements.

In a plating process for forming the slide surface construction, the basic conditions for a plating bath in carrying out an electrolytic Fe-plating process are as given in Table 1.

                  TABLE 1     ______________________________________     Plating bath     Ferrous sulfate (g/liter)                      pH     Temperature (°C.)     ______________________________________     100-400          5-7    10-60     ______________________________________

A pulse current process is mainly utilized as an energizing method. In the pulse current process, electric current I from a plating power source is controlled to describe a pulse waveform with the passage of time T, so that the current I is increased from a minimum current value Imin and reaches a maximum current value Imax, and is then dropped to the minimum current value Imin, as shown in FIG. 9.

If the energization time period from the start of the increasing of the electric current I to the start of the decreasing of the electric current I is represented by T_(ON), and a cycle time period is represented by T_(C), wherein one cycle is defined as being from the start of one current increasing to the start of the next current increasing, the ratio of the energization time period T_(ON) to the cycle time period T_(C), i.e., the time ratio T_(ON) /T_(C) preferably is set in a range of T_(ON) /T_(C) ≧0.45. The maximum cathode current density CDmax preferably is set in a range of CDmax≧2 A dm², and the average cathode current density CDm preferably is set in a range of CDm≧1 A dm².

If such a pulse current process is utilized, the ion concentration in the vicinity of a cathode is uniformized due to the fact that the maximum electric current alternately flows and does not flow in the plating bath. Thus, the composition of the slide surface construction 4 can be stabilized.

In the above-described electric Fe plating process, the precipitation and content (which indicates an amount present) of the (hhh) oriented Fe crystals or the (2hhh) oriented Fe crystals are controlled by changing the plating bath conditions and the energizing conditions. This control is easy under the utilization of the pulse current process and hence, the slide surface 4a is easily formed into an intended form.

The content of oxygen (O) in the slide surface construction is controlled mainly by the pH value and the temperature of the plating bath, but the maximum cathode current density CDmax, the average cathode density CDm and the like may be used as control factors. When phosphorus (P) is incorporated in the slide surface construction 4, a P-containing additive is added in an amount of 2 g/liter into the plating bath. The P-containing additives which may be used include substances which contain phosphorus and are soluble in water, such as sodium hypophosphite, potassium pyrophosphate, sodium dihydrogenphosphate and the like. The H content is controlled mainly by the temperature of the plating bath. When carbon (C) is incorporated in the slide surface construction 4, a C-containing additive is added in an amount of 2 g/liter into the plating bath. The C-containing additives which may be used include substances which contain carbon (C) and are soluble in water, such as saccharin, gelatin, ascorbic acid and the like. When boron (B) is incorporated in the slide surface construction 4, a B-containing additive is added in an amount of 30 g/liter into the plating bath. The B-containing additives which may be used include substances which contain boron (B) and which are soluble in water, such as boric acid, ammonium borate and the like.

The content of O, P, H, C and B contained in the slide surface construction 4 are extremely small. Therefore, in order to control each of these contents and to uniformly disperse these elements, a liquid replenisher adjusted to the same composition and the same temperature as those of the plating bath is supplied in a predetermined amount between the anode and the cathode during plating. If such supplying is not carried out, the pH value and temperature of the plating bath with regard to oxygen (O), the temperature of the plating bath with regard to hydrogen (H), and the concentration of each of the P-, C- and B-containing additives with regard to phosphorus (P), carbon (C) and boron (B), would be varied and for this reason, it would be difficult to control the content of O, P, H, C and B in the slide surface construction 4.

In addition to the electrolytic plating, examples of other plating processes are a PVD process, a CVD process, a sputtering process, an ion plating and the like, which are gas-phase plating processes. Conditions for carrying out the plating of tungsten (W) and molybdenum (Mo) by the sputtering process are as follows: for example, an AR gas pressure is in a range of 0.2 to 1 Pa; an average Ar gas accelerating electric power is in range of D.C. 1 to 1.5 kW; and a substrate temperature is in a range of 150° to 300° C. In this case, each of oxygen (O), phosphorus (P), carbon (C) and boron (B) can be incorporated in the slide surface construction 4 by a procedure which will be described below. With regard to oxygen (O), nitrous oxide (N₂ O) is sprayed onto a surface of a substrate at 0.1 to 5 SCCM (cc/min). With regard to phosphorus (P), hydrogen gas containing 5% of phosphine (PH₃) is sprayed onto a surface of a substrate at 0.1 to 5 SCCM (cc/min). With regard to carbon (C), ethylene gas is sprayed onto a surface of a substrate at 0.1 to 5 SCCM (cc/min). With regard to boron (B), hydrogen gas containing 5% of diborane (B₂ H₆) is sprayed onto a surface of a substrate at 0.1 to 5 SCCM (cc/min).

Conditions for carrying out the W-plating, by the CVD process are as follows: for example, a starting material is WF₆ ; a gas flow rate is in a range of 2 to 15 cc/min; a pressure within a chamber is in a range of 50 to 300 Pa; a substrate temperature is in a range of 400° to 600° C.; and an average output of ArF excimer laser is in a range of 5 to 40 W. In this case, each of oxygen (O), carbon (C) and boron (B) can be incorporated in the slide surface construction 4 by a procedure which will be described below. With regard to oxygen (O), nitrous oxide (N₂ O) is supplied to flow at 1 to 10 SCCM (cc/min) within a chamber. With regard to phosphorus (P), hydrogen gas containing 5% of phosphine (PH₃) is supplied to flow at 1 to 10 SCCM (cc/min) within a chamber. With regard to carbon (C), methane gas is supplied to flow at 1 to 10 SCCM (cc/min) within a chamber. With regard to boron (B), hydrogen gas containing 5% of diborane is supplied to flow at 1 to 10 SCCM (cc/min) within a chamber. When hydrogen (H) is incorporated in the slide surface construction 4, hydrogen is supplied to flow within a chamber during a gas-phase plating process.

First Embodiment

The first embodiment will be described as for a slide surface construction, which is formed of an aggregate of Fe crystals. In this slide surface construction, a large number of trigonal pyramid-shaped Fe crystals and/or a large number of hexagonal pyramid-shaped Fe crystals exist in a slide surface, and the aggregate contains at least one of oxygen (O) and phosphorus (P).

(Ia) Slide surface construction containing oxygen (O)

A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of the pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 15 μm.

Tables 2, 3, 4 and 5 show conditions for the electrolytic Fe-plating process for examples of the slide surface constructions; with Table 2 corresponding to the examples 1 to 5; with Table 3 corresponding to the examples 6 to 10; with Table 4 corresponding to the examples 11 to 15; and with Table 5 corresponding to the examples 16 to 20. The plating time was varied within a range of 5 to 60 minutes in order to set the thickness of the examples 1 to 20 at 15 μm, as described above. The amount of liquid replenisher supplied was set at 0.5 liters/min.

                  TABLE 2     ______________________________________     Slide  Plating bath     surface            Ferrous       Tem-  Pulse current process     con-   sulfate       perature                                CDmax CDm         T.sub.ON     struction            (g/liter)                    pH    (°C.)                                (A/dm.sup.2)                                      (A/dm.sup.2)                                            T.sub.ON T.sub.C                                                  (msec)     ______________________________________     Example 1            400     6     50    20    4     0.2   2     Example 2            400     6.3   50    20    4     0.2   2     Example 3            400     6     45    20    4     0.2   2     Example 4            400     6.3   43    20    4     0.2   2     Example 5            400     6.3   40    20    4     0.2   2     ______________________________________

                  TABLE 3     ______________________________________     Slide  Plating bath     surface            Ferrous       Tem-  Pulse current process     con-   sulfate       perature                                CDmax CDm         T.sub.ON     struction            (g/liter)                    pH    (°C.)                                (A/dm.sup.2)                                      (A/dm.sup.2)                                            T.sub.ON T.sub.C                                                  (msec)     ______________________________________     Example 6            300     6     50    20    4     0.2   2     Example 7            300     6     50    25    5     0.2   2     Example 8            300     6.3   45    20    4     0.2   2     Example 9            300     6.3   45    25    5     0.2   2     Example            300     6.3   45    30    6     0.2   2     10     ______________________________________

                  TABLE 4     ______________________________________     Slide  Plating bath     surface            Ferrous       Tem-  Pulse current process     con-   sulfate       perature                                CDmax CDm         T.sub.ON     struction            (g/liter)                    pH    (°C.)                                (A/dm.sup.2)                                      (A/dm.sup.2)                                            T.sub.ON T.sub.C                                                  (msec)     ______________________________________     Example            200     6     50    15    3     0.2   2     11     Example            200     6     50    25    5     0.2   2     12     Example            200     6.2   45    15    3     0.2   2     13     Example            200     6.3   45    15    3     0.2   2     14     Example            200     6.3   45    35    7     0.2   2     15     ______________________________________

                  TABLE 5     ______________________________________     Slide  Plating bath     surface            Ferrous       Tem-  Pulse current process     con-   sulfate       perature                                CDmax CDm         T.sub.ON     struction            (g/liter)                    pH    (°C.)                                (A/dm.sup.2)                                      (A/dm.sup.2)                                            T.sub.ON T.sub.C                                                  (msec)     ______________________________________     Example            100     6     50    15    3     0.2   2     16     Example            100     6     50    25    5     0.2   2     17     Example            100     6     45    25    5     0.2   2     18     Example            100     6.3   45    25    5     0.2   2     19     Example            100     6.5   45     8    1.6   0.2   2     20     ______________________________________

Tables 6, 7, 8 and 9 show the crystal form of the slide surface, the area rate A and grain size of the trigonal and/or hexagonal pyramid-shaped Fe crystals in the slide surface, the content (amount present) S of the oriented Fe crystals, the O content and the hardness of the section of the slide surface construction for the examples 1 to 20 of the slide surface constructions, with Table 6 corresponding to the examples 1 to 5; with Table 7 corresponding to the examples 6 to 10; with Table 8 corresponding to the examples 11 to 15; and with Table 9 corresponding to the examples 16 to 20.

                                      TABLE 6     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            O content     surface           slide                rate A                    size                        crystals            (% by                                                 Hardness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 HmV     __________________________________________________________________________     Example 1           Hexagonal                90  2-3 0.7 0.3 3.1 1.8 94.1                                            0.02 210           pyramid-           shaped     Example 2           Hexagonal                90  1-3 0.3 0.8 4.5 2   92.4                                            0.18 240           pyramid-           shaped     Example 3           Hexagonal                90  1-2 0.5 1.3 4.7 2.2 91.3                                            0.2  400           pyramid-           shaped     Example 4           Hexagonal                90  0.5-2                        0.6 1   4.9 2.6 90.9                                            0.4  470           pyramid-           shaped     Example 5           Hexagonal                90  0.5-1                        0.6 1.4 5.3 2   90.7                                            0.6  550           pyramid-           shaped     __________________________________________________________________________

                                      TABLE 7     __________________________________________________________________________                Trigonal, Hexagonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                         Content S (%) of oriented Fe                                             O content     surface           slide                rate A                    size crystals            (% by                                                  Hardness     construction           surface                (%) (μm)                         {110}                             {200}                                 {211}                                     {310}                                         {222}                                             weight)                                                  HmV     __________________________________________________________________________     Example 6           Hexagonal                60    1-5                         10.4                             8.2 12.5                                     8.2 60.7                                             0.02 190           and           trigonal           pyramid-           shaped     Example 7           Hexagonal                60    1-5                         11.2                             7.9 11.8                                     8.8 60.3                                             0.18 230           and           trigonal           pyramid-           shaped     Example 8           Hexagonal                60  0.5-4                         9.9 7.3 11.7                                     8.8 62.3                                             0.2  380           and           trigonal           pyramid-           shaped     Example 9           Hexagonal                60  0.5-3                         10.7                             6   13.1                                     8.4 61.8                                             0.4  400           and           trigonal           pyramid-           shaped     Example 10           Hexagonal                60  0.5-2                         11.5                             8.4 12.4                                     6.5 61.2                                             0.6  450           and           trigonal           pyramid-           shaped     __________________________________________________________________________

                                      TABLE 8     __________________________________________________________________________                Trigonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            O content     surface           slide                rate A                    size                        crystals            (% by                                                 Hardness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 HmV     __________________________________________________________________________     Example 11           Trigonal                40  0.5-6                        16.8                            14.4                                16.3                                    10.5                                        42  0.02 200           pyramid-           shaped     Example 12           Trigonal                40  0.5-6                        17.5                            13.9                                16  10.9                                        41.7                                            0.18 240           pyramid-           shaped     Example 13           Trigonal                40  0.5-4                        20.2                            12.5                                16.7                                    9.7 40.9                                            0.2  360           pyramid-           shaped     Example 14           Trigonal                40  0.5-2                        20.6                            12  16.8                                    9.4 41.2                                            0.4  390           pyramid-           shaped     Example 15           Trigonal                40  0.5-2                        21.3                            11.1                                17.6                                    9   41  0.6  410           pyramid-           shaped     __________________________________________________________________________

                                      TABLE 9     __________________________________________________________________________                Trigonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            O content     surface           slide                rate A                    size                        crystals            (% by                                                 Hardness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 HmV     __________________________________________________________________________     Example 16           Trigonal                35  0.5-5                        19.6                            9.2 22.5                                    13.8                                        34.9                                            0.02 180           pyramid-           shaped     Example 17           Trigonal                35  0.5-5                        19.9                            11.4                                20.8                                    13.3                                        34.6                                            0.18 220           pyramid-           shaped     Example 18           Trigonal                35  0.5-5                        19.5                            12.1                                21.7                                    12.4                                        34.3                                            0.2  370           pyramid-           shaped     Example 19           Trigonal                35  0.5-5                        19.4                            11.2                                21.3                                    12.9                                        35.2                                            0.4  390           pyramid-           shaped     Example 20           Trigonal                35  0.5 20.1                            13  19.6                                    13.6                                        33.7                                            0.6  400           pyramid-           shaped     __________________________________________________________________________

The area rate A of trigonal and/or hexagonal pyramid-shaped Fe crystals was determined according to an equation, A=(c/b)×100(%), wherein b represents the area of the slide surface, and c represents an area occupied in the slide surface by all of the trigonal and/or hexagonal pyramid-shaped Fe crystals. The grain size of the hexagonal pyramid-shaped Fe crystals is an average value of distances between opposed corners on opposite sides of an apex, i.e., of lengths of three diagonal lines. The grain size of the trigonal pyramid-shaped Fe crystals is an average value of distances from each corner via an apex to each opposed side, i.e., three distances.

The content S was determined by the following method based on X-ray diffraction patterns (wherein X-ray was applied in a direction perpendicular to the slide surface) for the examples 1 to 20. FIG. 10 is an X-ray diffraction pattern for the example 4. For example, the {110} oriented Fe crystal means an oriented Fe crystal with its {110} plane oriented toward the slide surface 4a.

{110} Oriented Fe crystals: S₁₁₀ ={(I₁₁₀ /IA₁₁₀)/T}×100

{200} Oriented Fe crystals: S₂₀₀ ={(I₂₀₀ /IA₂₀₀)/T}×100

{211} Oriented Fe crystals: S₂₁₁ ={(I₂₁₁ /IA₂₁₁)/T}×100

{310} Oriented Fe crystals: S₃₁₀ ={(I₃₁₀ /IA₃₁₀)/T}×100

{222} Oriented Fe crystals: S₂₂₂ ={(I₂₂₂ /IA₂₂₂)/T}×100

wherein each of I₁₁₀, I₂₀₀, I₂₁₁, I₃₁₀ and I₂₂₂ is a measurement (cps) of an intensity of X-ray reflected from each crystal plane; each of IA₁₁₀, IA₂₀₀, IA₂₁₁, IA₃₁₀ and IA₂₂₂ is an intensity ratio of X-rays reflected from crystal planes in an ASTM card, IA₁₁₀ =100; IA₂₀₀ =20; IA₂₁₁ =30; IA₃₁₀ =12; and IA₂₂₂ =6. Further, T=(I₁₁₀ /IA₁₁₀)+(1₂₀₀ /IA₂₀₀)+(I₂₁₁ /IA₂₁₁)+(I₃₁₀ /IA₃₁₀)+(I₂₂₂ /IA₂₂₂).

FIGS. 11A and 11B are photomicrographs showing the crystal structure of the example 4. As shown in FIG. 11A, a large number of hexagonal pyramid-shaped Fe crystals are observed in the slide surface, and as shown in FIG. 11B, a large number of columnar Fe crystals are observed in the vertical section of the slide surface construction. In this case, the area rate A of the hexagonal pyramid-shaped Fe crystals is equal to 90%, as given in Table 6. The columnar Fe crystals and thus the hexagonal pyramid-shaped Fe crystals are {222} oriented Fe crystals with their (hhh) plane, i.e., {222} plane oriented toward the slide surface. The content S of the {222} oriented Fe crystals is equal to 90.9%, as shown in Table 6 and FIG. 10.

The measurement of the O content was carried out by a procedure which comprises peeling-off each of the examples 1 to 20 from the substrate 2 and then subjecting each example to an analysis according to an inert gas melting/thermal conductimetry (JIS Z2613).

FIG. 12 is a graph illustrating the relationship between the O content and the hardness for the examples 1 to 5. In FIG. 12, points (1) to (5) correspond to the examples 1 to 5, respectively. The relation between the point and the example applies to the Figures which will be described hereinafter. It can be seen from FIG. 12 that if the O content is set in a range of O≧0.2% by weight, the hardness is suddenly increased. The same is true of the examples 6 to 20, as set forth in Tables 7, 8 and 9.

Then, chips of the examples 1 to 20 were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 10. Conditions for the seizure test are as follows: The material for a disk is an Al--Si (10% by weight) alloy; the peripheral speed of the disk is 15 m/sec; the amount of oil supplied is 0.3 ml/min; and the area of the slide surface of the chip is 1 cm².

                  TABLE 10     ______________________________________               Seizure                Seizure     Slide surface               generating   Slide surface                                      generating     construction               load (N)     construction                                      load (N)     ______________________________________     Example 1 1200         Example 11                                      800     Example 2 1300         Example 12                                      850     Example 3 2050         Example 13                                      1600     Example 4 2150         Example 14                                      1750     Example 5 2300         Example 15                                      1850     Example 6 1010         Example 16                                      250     Example 7 1100         Example 17                                      300     Example 8 1800         Example 18                                      600     Example 9 1950         Example 19                                      650     Example 10               2100         Example 20                                      700     ______________________________________

FIG. 13 illustrates the relationship between the O content and the seizure generating load for the examples 1 to 20, and FIG. 14 illustrates the relationship between the area rate A of the trigonal and/or hexagonal pyramid-shaped Fe crystals and the seizure generating load for the examples 1 to 20.

If the examples 1 to 5 are compared with one another in FIG. 13, they have the same area rate A of the hexagonal pyramid-shaped Fe crystals and the initially equivalent oil retention, but the examples 3 to 5 have the O content equal to or higher than 0.2% by weight and the hardness higher than those of the examples 1 and 2. Therefore, the examples 3 to 5 exhibit an excellent wear resistance and hence, the oil retention thereof is maintained. Consequently, the examples 3 to 5 have a seizure resistance superior to the examples 1 and 2. The same is true of a comparison between the examples 8 to 10 and the examples 6 and 7; between the examples 13 to 15 and the examples 11 and 12; and between the examples 18 to 20 and the examples 16 and 17. From this, it can be seen that in order to enhance the seizure resistance, the O content may be set in a range of O≧0.2% by weight, if the area rate A is constant.

If the examples 5, 10, 15 and 20 are compared with one another in FIG. 14, they have the same O content, but the examples 5, 10 and 15 have a better oil retention than that of the example 20, because the area rate A is equal to or higher than 40%. Consequently, the examples 5, 10 and 15 have a seizure resistance superior to the example 20. The same is true of a comparison between the examples 4, 9 and 14 and the example 19; between the examples 3, 8 and 13 and the example 18; between the examples 2, 7 and 12 and the example 17; and between the examples 1, 6 and 11 and the example 16. From this, it can be seen that in order to enhance the seizure resistance, the area rate A may be set in a range of A≧40%, if the O content is constant.

Therefore, it can be concluded that it is required for the slide surface construction 4 capable of withstanding a severe sliding environment to have requirements of an area rate A≧40% and an O content≧0.2% by weight. These requirements are satisfied by the examples 3 to 5, 8 to 10, and 13 to 15. Consequently, the seizure generating surface pressure for these examples is equal to or larger than 1600N and remarkably high, as compared with those of the other examples.

(Ib) Slide surface construction containing phosphorus (P)

A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of a pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 15 μm.

Tables 11, 12, 13 and 14 show conditions for the electrolytic Fe-plating process for examples of the slide surface constructions; with Table 11 corresponding to the examples 1 to 4; with Table 12 corresponding to the examples 5 to 8; with Table 13 corresponding to the examples 9 to 12; and with Table 14 corresponding to the examples 13 to 16. The plating time was varied within a range of 5 to 60 minutes in order to set the thickness of the examples 1 to 16 at 15 μm, as described above. The amount of liquid replenisher supplied was set at 0.5 liters/min.

                                      TABLE 11     __________________________________________________________________________     Plating bath     Slide Composition (g/liter)                              Pulse current process     surface           Ferrous               Sodium   Temperature                              CDmax                                  CDm     T.sub.ON     construction           sulfate               hypophosphite                      pH                        (°C.)                              (A/dm.sup.2)                                  (A/dm.sup.2)                                      T.sub.ON /T.sub.C                                          (msec)     __________________________________________________________________________     Example 1           400 1      6 50    10  2   0.2 2     Example 2           400 1      6 50    12.5                                  2.5 0.2 2     Example 3           400 2      6 50    15  3   0.2 2     Example 4           400 2      6 50    20  4   0.2 2     __________________________________________________________________________

                                      TABLE 12     __________________________________________________________________________     Plating bath     Slide Composition (g/liter)                              Pulse current process     surface           Ferrous               Sodium   Temperature                              CDmax                                  CDm     T.sub.ON     construction           sulfate               hypophosphite                      pH                        (°C.)                              (A/dm.sup.2)                                  (A/dm.sup.2)                                      T.sub.ON /T.sub.C                                          (msec)     __________________________________________________________________________     Example 5           300 1      6 50    10  2   0.2 2     Example 6           300 1      6 50    12.5                                  2.5 0.2 2     Example 7           300 2      6 50    15  3   0.2 2     Example 8           300 2      6 50    20  4   0.2 2     __________________________________________________________________________

                                      TABLE 13     __________________________________________________________________________     Plating bath     Slide Composition (g/liter)                              Pulse current process     surface           Ferrous               Sodium   Temperature                              CDmax                                  CDm     T.sub.ON     construction           sulfate               hypophosphite                      pH                        (°C.)                              (A/dm.sup.2)                                  (A/dm.sup.2)                                      T.sub.ON /T.sub.C                                          (msec)     __________________________________________________________________________     Example 9           200 1      6 50    10  2   0.2 2     Example 10           200 1      6 50    12.5                                  2.5 0.2 2     Example 11           200 2      6 50    15  3   0.2 2     Example 12           200 2      6 50    17.5                                  3.5 0.2 2     __________________________________________________________________________

                                      TABLE 14     __________________________________________________________________________     Plating bath     Slide Composition (g/liter)                              Pulse current process     surface           Ferrous               Sodium   Temperature                              CDmax                                  CDm     T.sub.ON     construction           sulfate               hypophosphite                      pH                        (°C.)                              (A/dm.sup.2)                                  (A/dm.sup.2)                                      T.sub.ON /T.sub.C                                          (msec)     __________________________________________________________________________     Example 13           100 1      6 50    10  2   0.2 2     Example 14           100 1      6 50    12.5                                  2.5 0.2 2     Example 15           100 2      6 50    17.5                                  3.5 0.2 2     Example 16           100 2      6 50    20  4   0.2 2     __________________________________________________________________________

Tables 15, 16, 17 and 18 show the crystal form of the slide surface, the area rate A and grain size of the trigonal and/or hexagonal pyramid-shaped Fe crystals in the slide surface, the content S (which indicates the amount present) of oriented Fe crystals, the P content and the hardness of a section of the slide surface construction for the examples 1 to 16. Table 15 corresponds to the examples 1 to 4; Table 16 corresponds to the examples 5 to 8; Table 17 corresponds to the examples 9 to 12; and Table 18 corresponds to the examples 13 to 16.

                                      TABLE 15     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            P content     surface           slide                rate A                    size                        crystals            (% by                                                 Hardness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 HmV     __________________________________________________________________________     Example 1           Hexagonal                90  0.5-6                        0.7 0   5.3 0   94  0.01 240           pyramid-           shaped     Example 2           Hexagonal                90  0.5-5                        2.1 0   4.5 1.8 91.6                                            0.035                                                 260           pyramid-           shaped     Example 3           Hexagonal                90  0.5-4                        1.2 0   7.2 0   91.6                                            0.04 440           pyramid-           shaped     Example 4           Hexagonal                90  0.5-3                        0   0   9.4 0   90.6                                            0.12 490           pyramid-           shaped     __________________________________________________________________________

                                      TABLE 16     __________________________________________________________________________                Trigonal,                Hexagonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            P content     surface           slide                rate A                    size                        crystals            (% by                                                 Hardness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 HmV     __________________________________________________________________________     Example 5           Hexagonal                60  0.5-5                        16.2                            0   18.5                                    2.5 62.8                                            0.01 220           and           trigonal           pyramid-           shaped     Example 6           Hexagonal                60  0.5-5                        15.7                            0   20.7                                    3.1 60.5                                            0.035                                                 250           and           trigonal           pyramid-           shaped     Example 7           Hexagonal                60  0.5-4                        16.1                            0   19.7                                    2.8 61.4                                            0.04 450           and           trigonal           pyramid-           shaped     Example 8           Hexagonal                60  0.5-4                        19  0   17.9                                    3   60.1                                            0.12 500           and           trigonal           pyramid-           shaped     __________________________________________________________________________

                                      TABLE 17     __________________________________________________________________________                Trigonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            P content     surface           slide                rate A                    size                        crystals            (% by                                                 Hardness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 HmV     __________________________________________________________________________     Example 9           Trigonal                40  0.5-6                        25.3                            0   30.6                                    3.6 40.5                                            0.01 210           pyramid-           shaped     Example 10           Trigonal                40  0.5-6                        22  0   33.7                                    3.9 40.4                                            0.035                                                 240           pyramid-           shaped     Example 11           Trigonal                40  0.5-6                        19.7                            0   35.2                                    4.4 40.7                                            0.04 450           pyramid-           shaped     Example 12           Trigonal                40  0.5-5                        17.7                            0   36.7                                    4.8 40.8                                            0.12 510           pyramid-           shaped     __________________________________________________________________________

                                      TABLE 18     __________________________________________________________________________                Trigonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            P content     surface           slide                rate A                    size                        crystals            (% by                                                 Hardness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 HmV     __________________________________________________________________________     Example 13           Trigonal                35  0.5-5                        20.4                            9.4 23.4                                    12.2                                        34.6                                            0.01 280           pyramid-           shaped     Example 14           Trigonal                35  0.5-5                        18.9                            10.5                                26.3                                    10.1                                        34.2                                            0.035                                                 310           pyramid-           shaped     Example 15           Trigonal                35  0.5-6                        18.2                            10.8                                25.7                                    10.4                                        34.9                                            0.04 340           pyramid-           shaped     Example 16           Trigonal                35  0.5-6                        19.1                            11.2                                25.6                                    9.8 34.3                                            0.12 360           pyramid-           shaped     __________________________________________________________________________

The area rate A, the grain size and the content S were determined in a manner similar to that for the examples 1-20 section (Ia) above. FIG. 15 is an X-ray diffraction pattern for the example 4.

FIG. 16 is a photomicrograph showing the crystal structure of the slide surface of the example 4, wherein a large number of hexagonal pyramid-shaped Fe crystals are observed. In this case, as shown in Table 15, the area rate A of the hexagonal pyramid-shaped Fe crystals is equal to 90%. The hexagonal pyramid-shaped Fe crystals are {222} oriented Fe crystals, and the content S of the {222} oriented Fe crystals is equal to 90.6%, as shown in Table 15 and FIG. 15.

The measurement of the P content was carried out by a procedure which comprises peeling off each of the examples 1 to 16 from the substrate 2 and subjecting each example to a molybdic acid blue absorptiometric analysis (JIS G1214).

FIG. 17 is a graph illustrating the relationship between the P content and the hardness for the examples 1 to 4. It can be seen from FIG. 17 that if the P content is set in a range of P≧0.04% by weight, the hardness is suddenly increased. The same is true of the examples 5 to 16.

Then, chips of the examples 1 to 16 were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 19. Conditions for the seizure test are identical to those described in section (Ia).

                  TABLE 19     ______________________________________               Seizure                Seizure     Slide surface               generating   Slide surface                                      generating     construction               load (N)     construction                                      load (N)     ______________________________________     Example 1 1200         Example 9 800     Example 2 1300         Example 10                                      880     Example 3 2100         Example 11                                      1500     Example 4 2350         Example 12                                      1650     Example 5 1050         Example 13                                      320     Example 6 1120         Example 14                                      400     Example 7 1800         Example 15                                      600     Example 8 1980         Example 16                                      680     ______________________________________

FIG. 18 illustrates the relationship between the P content and the seizure generating load for the examples 1 to 16, and FIG. 19 illustrates the relationship between the area rate A of the trigonal and/or hexagonal pyramid-shaped Fe crystals and the seizure generating load for the examples 1 to 16.

If the examples 1 to 4 are compared with one another in FIG. 18, they have the same area rate A of the hexagonal pyramid-shaped Fe crystals and the initially equivalent oil retention, but the examples 3 and 4 have the P content equal to or higher than 0.04% by weight, and the hardness higher than those of the examples 1 and 2. Therefore, the examples 3 and 4 exhibit an excellent wear resistance and hence, the oil retention thereof is maintained. Consequently, the examples 3 and 4 have a seizure resistance superior to the examples 1 and 2. The same is true of a comparison between the examples 7 and 8 and the examples 5 and 6; between the examples 11 and 12 and the examples 9 and 10; and between the examples 15 and 16 and the examples 13 and 14. From this, it can be seen that in order to enhance the seizure resistance, the P content may be set in a range of P≧0.04% by weight, if the area rate A is constant.

If the examples 4, 8, 12 and 16 are compared with one another in FIG. 19, they have the same P content, but examples 4, 8 and 12 have a better oil retention than that of the example 16, because the area rate A is equal to or higher than 40%. Consequently, the examples 4, 8 and 12 have an excellent seizure resistance, as compared with the example 16. The same is true of a comparison between the examples 3, 7 and 11 and the example 15; between the examples 2, 6 and 10 and the example 14; and between the examples 1, 5 and 9 and the example 13. From this, it can be seen that in order to enhance the seizure resistance, the area rate A may be set in a range of A≧40%, if the P content is constant.

Therefore, it can be concluded that it is required for the slide surface construction 4 capable of withstanding a severe sliding environment to have requirements of an area rate A≧40% and an P content≧0.04% by weight. These requirements are satisfied by the examples 3, 4, 7, 8, 11 and 12. Consequently, the seizure generating surface pressure for these examples is equal to or larger than 1500N and remarkably high, as compared with those of the other examples. (Ic) Slide surface construction containing oxygen and phosphorus A piston pin 1 for an internal combustion engine was produced by subjecting an outer peripheral surface 3 of a pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 15 μm.

Table 20 shows conditions for the electrolytic Fe-plating process for example 1 of the slide surface construction. The plating time was set at 15 minutes, and the amount of liquid replenisher supplied was set at 0.5 liters/min.

                                      TABLE 20     __________________________________________________________________________     Plating bath     Slide Composition (g/liter)                              Pulse current process     surface           Ferrous               Sodium   Temperature                              CDmax                                  CDm     T.sub.ON     construction           sulfate               hypophosphite                      pH                        (°C.)                              (A/dm.sup.2)                                  (A/dm.sup.2)                                      T.sub.ON /T.sub.C                                          (msec)     __________________________________________________________________________     Example 1           400 0.8    6 45    20  4   0.2 2     __________________________________________________________________________

Table 21 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the content S of the oriented Fe crystals, the O content, the P content and the hardness of a section of the slide surface construction for the example.

                                      TABLE 21     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            O content                                                 P content     surface           slide                rate A                    size                        crystals            (% by                                                 (% by                                                      Hardness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 weight)                                                      HmV     __________________________________________________________________________     Example 1           Hexagonal                90  0.5-3                        1.7 0.5 5   1.6 91.2                                            0.2  0.04 465           pyramid-           shaped     __________________________________________________________________________

The area rate A, the grain size and the content S were determined in the same manner as in section (Ia) above. The O content was determined in the same manner as in section (Ia), and the P content was determined in the same manner as in section (Ib).

As can be seen from the comparison of the example 1 in Table 21 with the example 3 in Table 6 and the example 3 in Table 15, if the slide surface construction contains both oxygen (O) and phosphorus (P) in contents in a range of O≧0.2% by weight and in a range of P≧0.04% by weight, respectively, the hardness is increased more than that of the slide surface construction containing only oxygen or phosphorus.

Then, chips of the example were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load. The result showed a seizure generating load of 2500N. Conditions for the seizure test are identical to those described in section (Ia).

As can be seen from the comparison of this example 1 with the example 3 in Table 10 and the example 3 in Table 19, the example 1 has a seizure resistance superior to the examples 3 in Tables 10 and 19, as a result of increasing of the hardness.

Of course, it is required that the area rate A of the hexagonal pyramid-shaped Fe crystals in the slide surface is in a range of A≧40% even with the slide surface construction containing both of oxygen (O) and phosphorus (P), as described above.

Second Embodiment

The second embodiment will be described as for a slide surface construction, which is formed of an aggregate of Fe crystals. In this slide surface construction, a large number of hexagonal pyramid-shaped Fe crystals exist in a slide surface, and the aggregate contains at least one of oxygen (O) and phosphorus (P), and at least one of hydrogen (H) and carbon (C). (IIa) Slide surface construction containing oxygen (O) and at least one of hydrogen (H) and carbon (C)

A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 15 μm.

Table 22 shows conditions for the electrolytic Fe-plating process for examples 1 to 3 of the slide surface constructions. The plating time was varied within a range of 5 to 60 minutes in order to set the thickness of the examples 1 to 3 at 15 μm, as described above. The amount of liquid replenisher supplied was set at 0.5 liters/min.

                                      TABLE 22     __________________________________________________________________________     Plating bath     Slide Composition (g/liter)                             Pulse current process     surface           Ferrous     Temperature                             CDmax                                 CDm     T.sub.ON     construction           sulfate               Saccharine                     pH                       (°C.)                             (A/dm.sup.2)                                 (A/dm.sup.2)                                     T.sub.ON /T.sub.C                                         (msec)     __________________________________________________________________________     Example 1           400 0     6.5                       45    20  4   0.2 2     Example 2           400 0.75  6.5                       50    40  8   0.2 2     Example 3           400 0.75  6.5                       45    40  8   0.2 2     __________________________________________________________________________

Table 23 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the content (amount present) S of the oriented Fe crystals, the O content, H content, the C content and the hardness of the section of the slide surface construction for the examples 1 to 3 of the slide surface constructions.

                                      TABLE 23     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals                 O   H   C     Slide form of                Area                    Grain                        Content S (%) of oriented                                            content                                                content                                                    content                                                        Hard-     surface           slide                rate A                    size                        Fe crystals         (% by                                                (% by                                                    (% by                                                        ness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                weight)                                                    weight)                                                        HmV     __________________________________________________________________________     Example 1           Hexagonal                90    1-2                        0.6 2.3 5.2 1.9 90  0.2 0.01                                                    very                                                        430           pyramid-                                 small           shaped     Example 2           Hexagonal                90    1-2                        0.8 1.1 5.7 2.1 90.3                                            0.2 very                                                    0.03                                                        430           pyramid-                             small           shaped     Example 3           Hexagonal                90  0.5-3                        0.4 1.2 4.9 1.7 91.8                                            0.2 0.01                                                    0.03                                                        460           pyramid-           shaped     __________________________________________________________________________

The area rate A, the grain size, the content S and the O content were determined in the same manner as in section (Ia) above. The measurement of the H content was carried out by a procedure which comprises peeling-off each of the examples 1 to 3 from the substrate 2 and then subjecting each example to an analysis according to an inert gas melting/thermal conductimetry (JIS Z2614). The measurement of the C content was carried out by a procedure which comprises peeling-off each of the examples 1 to 3 from the substrate 2 and then subjecting each example to an analysis according to an infrared absorptiometry (JIS G1211). The term "very small" for the H content in Table 23 indicates, for example, about 0.005% by weight, and the term "very small" for the C content in Table 23 indicates, for example, about 0.008% by weight. The same is true of Tables which will be described hereinafter.

As can be seen from the comparison of the examples 1 to 3 in Table 23 with the example 3 in Table 6, if the H and C contents are set in ranges of H≧0.01% by weight and C≧0.03% by weight, respectively when O≧0.2% by weight, the hardness is increased more than that of the slide surface construction containing only oxygen (O). It can be also seen from Table 23 that the example 3 containing O, H and C has the highest hardness.

Then, chips of the examples 1 to 3 were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 24. Conditions for the seizure test are identical to those described in the item (Ia).

                  TABLE 24     ______________________________________     Slide surface construction                     Seizure generating load (N)     ______________________________________     Example 1       2150     Example 2       2200     Example 3       2400     ______________________________________

FIG. 20 is a graph illustrating the relationship between the contained elements and the seizure generating load for the examples 1 to 3. As is apparent from Table 24 and FIG. 20, for the examples 1 to 3, the seizure generating load is largely increased with such an increase in hardness as described above, as compared with the example 3 in Table 10. The example 2 containing oxygen (O) and carbon (C) has a seizure resistance superior to the example 1 containing oxygen (O) and hydrogen (H). Further, the seizure generating load for the example 3 containing oxygen (O), hydrogen (H) and carbon (C) is highest.

Then, a disk of the example 1 was fabricated and subjected to a sliding test in a chip-on-disk manner under lubrication. Conditions for the sliding test are as follows: The material for the chip was JIS FC250; the material for the disk was Al--Si (10% by weight) alloy; the peripheral speed of the disk was 15 m/sec; the amount of oil supplied was 40 cc/min; the area of the slide surface of the chip was 2 cm² ; and the pressure on the chip was 10 MPa.

FIG. 21 is a photomicrograph showing the crystal structure of a vertical section of the example after being subjected to the sliding test. As is apparent from FIG. 21, for the example 1, the area rate A of the hexagonal pyramid-shaped Fe crystals is equal to 90%, and the H content is equal to 0.01% by weight. Therefore, tip ends of the hexagonal pyramid-shaped Fe crystals are sheared and worn into a trapezoidal shape. Thus, the surface-on-surface sliding is permitted to occur and hence, the friction coefficient μ is reduced, thereby providing an excellent sliding characteristic.

Of course, even for the slide surface construction containing at least one of oxygen (O), hydrogen (H) and carbon (C), as described above, it is required that the area rate A of the hexagonal pyramid-shaped Fe crystals in the slide surface is equal to or higher than 40%. (IIb) Slide surface construction containing at least one of phosphorus (P), hydrogen (H) and carbon (C)

A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of a pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 15 μm.

Table 25 shows conditions for the electrolytic Fe-plating process for examples of the slide surface constructions. The plating time was varied within a range of 5 to 60 minutes in order to set the thickness of the examples 1 to 3 at 15 μm, as described above. The amount of liquid replenisher supplied was set at 0.5 liters/min.

                                      TABLE 25     __________________________________________________________________________     Plating bath     Composition (g/liter)        Pulse current process     Slide surface           Ferrous               Sodium hypo-  Tempera-                                  CDmax                                      CDm     T.sub.ON     construction           sulfate               phosphite                      Saccharine                           pH                             ture (°C.)                                  (A/dm.sup.2)                                      (A/dm.sup.2)                                          T.sub.ON /T.sub.C                                              (msec)     __________________________________________________________________________     Example 1           400 0.8    0    6.3                             48   20  4   0.2 2     Example 2           400 0.5    0.75 6.3                             50   40  8   0.2 2     Example 3           400 0.5    0.75 6.3                             48   40  8   0.2 2     __________________________________________________________________________

Table 26 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the content (amount present) S of the oriented Fe crystals, the P content, the H content, the C content and the hardness of a section of the slide surface construction for the examples 1 to 3 of slide surface constructions.

                                      TABLE 26     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals                 P   H   C     Slide form of                Area                    Grain                        Content S (%) of oriented                                            content                                                content                                                    content                                                        Hard-     surface           slide                rate A                    size                        Fe crystals         (% by                                                (% by                                                    (% by                                                        ness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                weight)                                                    weight)                                                        HmV     __________________________________________________________________________     Example 1           Hexagonal                90  0.5-3                        2.7 0.2 4.4 1.5 91.2                                            0.04                                                0.01                                                    very                                                        450           pyramid-                                 small           shaped     Example 2           Hexagonal                90  0.5-3                        2.7 0.1 4.5 1.7 91  0.04                                                very                                                    0.03                                                        455           pyramid-                             small           shaped     Example 3           Hexagonal                90  0.5-3                        2.5 0.4 4.6 1.7 90.8                                            0.04                                                0.01                                                    0.03                                                        470           pyramid-           shaped     __________________________________________________________________________

As is apparent from the comparison of the examples 1 to 3 in Table 26 with the example 3 in Table 15, if the H content and/or the C content are set in ranges of H≧0.01% by weight and C≧0.03% by weight when P≧0.04% by weight, the hardness is increased more than that of the slide surface construction containing only phosphorus. It is also apparent from Table 26 that the example 2 containing phosphorus (P) and carbon (C) has a higher hardness than that of the example 1 containing phosphorus (P) and hydrogen (H), and that the example 3 containing phosphorus (P), hydrogen (H) and carbon (C) has the highest hardness.

Then, chips of the examples 1 to 3 were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 27. Conditions for the seizure test are identical to those described in section (Ia).

                  TABLE 27     ______________________________________     Slide surface construction                     Seizure generating load (N)     ______________________________________     Example 1       2250     Example 2       2300     Example 3       2500     ______________________________________

FIG. 22 is a graph illustrating the relationship between the contained elements and the seizure generating load for the examples 1 to 3. As is apparent from Table 27 and FIG. 22, for the examples 1 to 3, the seizure generating load is largely increased with such an increase in hardness described above, as compared with the example 3 in Table 19. The example 2 containing phosphorus (P) and carbon (C) has a seizure resistance superior to the example 1 containing phosphorus (P) and hydrogen (H), and the seizure generating load for the example 3 containing phosphorus (P), hydrogen (H) and carbon (C) is the highest.

Of course, even for the slide surface construction containing at least one of phosphorus (P), hydrogen (H) and carbon (C), as described above, it is required that the area rate A of the hexagonal pyramid-shaped Fe crystals in the slide surface is equal to or higher than 40%. (IIc) Slide surface construction containing oxygen (O) and phosphorus (P), and at least one of hydrogen (H) and carbon (C)

A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of a pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 15 μm.

Table 28 shows conditions for the electrolytic Fe-plating process for examples 1 to 3 of the slide surface constructions 4. The plating time was varied within a range of 5 to 60 minutes in order to set the thickness of the examples 1 to 3 at 15 μm, as described above. The amount of liquid replenisher supplied was set at 0.5 liters/min.

                                      TABLE 28     __________________________________________________________________________     Plating bath     Composition (g/liter)        Pulse current process     Slide surface           Ferrous               Sodium hypo-  Tempera-                                  CDmax                                      CDm     T.sub.ON     construction           sulfate               phosphite                      Saccharine                           pH                             ture (°C.)                                  (A/dm.sup.2)                                      (A/dm.sup.2)                                          T.sub.ON /T.sub.C                                              (msec)     __________________________________________________________________________     Example 1           400 0.8    0    6.5                             45   20  4   0.2 2     Example 2           400 0.5    0.75 6.5                             50   40  8   0.2 2     Example 3           400 0.5    0.75 6.5                             45   40  8   0.2 2     __________________________________________________________________________

Table 29 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the content (amount present) S of the oriented Fe crystals, the O content, the P content, the H content, the C content and the hardness of a section of the slide surface construction for the examples 1 to 3 of slide surface constructions.

                                      TABLE 29     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            O content                                                 P content                                                      H content                                                           C                                                                Hard-nt     surface           slide                rate A                    size                        crystals            (% by                                                 (% by                                                      (% by                                                           (%                                                                ness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 weight)                                                      weight)                                                           weight)                                                                HmV     __________________________________________________________________________     Example 1           Hexagonal                90  0.5-3                        2   0.4 5.2 1.5 90.9                                            0.2  0.04 0.01 very 480           pyramid-                                        small           shaped     Example 2           Hexagonal                90  0.5-3                        1.7 0.7 4.6 1.7 91.3                                            0.2  0.04 very 0.03 485           pyramid-                                   small           shaped     Example 3           Hexagonal                90  0.5-2                        2.3 0.5 4.9 1.7 90.6                                            0.2  0.04 0.01 0.03 510           pyramid-           shaped     __________________________________________________________________________

The area rate A, the grain size and the content S were determined in the same manner as in section (Ia) above. The O content was determined in the same manner as in section (Ia); the P content was determined in the same manner as in section (Ib), and the H and C contents were determined in the same manner as in section (IIa).

As is apparent from the comparison of the examples 1 to 3 in Table 29 with the example 1 in Table 21, if the H content and/or the C content are set in ranges of H≧0.01% by weight and C≧0.03% by weight when O≧0.2% by weight, and P≧0.04% by weight, the hardness is increased more than that of the slide surface construction containing oxygen (O) and phosphorus (P) in those ranges. It is also apparent from Table 29 that the example 2 containing oxygen (O), phosphorus (P) and carbon (C) has a higher hardness than that of the example 1 containing oxygen (O), phosphorus (P) and hydrogen (H), and the example 3 containing oxygen (O), phosphorus (P), hydrogen (H) and carbon (C) has the highest hardness.

Then, chips of the examples 1 to 3 were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 30. Conditions for the seizure test are identical to those in section (Ia).

                  TABLE 30     ______________________________________     Slide surface construction                     Seizure generating load (N)     ______________________________________     Example 1       2600     Example 2       2650     Example 3       2900     ______________________________________

FIG. 23 is a graph illustrating the relationship between the contained elements and the seizure generating load for the examples 1 to 3. As is apparent from Table 30 and FIG. 23, for the examples 1 to 3, the seizure generating load is largely increased with such an increase in hardness described above, as compared with the example 1 described in section (Ic). The example 2 containing oxygen (O), phosphorus (P) and carbon (C) has a seizure resistance superior to the example 1 containing oxygen (O), phosphorus (P) and hydrogen (H), and the seizure generating load for the example 3 containing oxygen (O), phosphorus (P), hydrogen (H) and carbon (C) is the highest.

Of course, even for the slide surface construction containing at least one of oxygen (O), phosphorus (P), and at least one of hydrogen (H) and carbon (C), as described above, it is required that the area rate A of the hexagonal pyramid-shaped Fe crystals in the slide surface is equal to or higher than 40%.

Third Embodiment

The third embodiment will be described as for a slide surface construction, which is formed of an aggregate of Fe crystals. In this slide surface construction, the aggregate has a large number of columnar Fe crystals which are grown from a substrate and whose tip ends are formed of hexagonal pyramid-shaped Fe crystals. The hexagonal pyramid-shaped Fe crystals exist in the slide surface, and further, the aggregate contains at least one of oxygen (O) and phosphorus (P), and boron (B).

A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 20 μm.

Table 31 shows conditions for the electrolytic Fe-plating process for examples 1 to 3 of the slide surface constructions. The plating time was varied within a range of 10 to 60 minutes in order to set the thickness of the examples 1 to 3 at 20 μm, as described above. The amount of liquid replenisher supplied was set at 0.5 liters/min.

                                      TABLE 31     __________________________________________________________________________     Plating bath     Composition (g/liter)      Pulse current process     Slide surface           Ferrous               Boric                  Sodium   Tempera-                                CDmax                                    CDm     T.sub.ON     construction           sulfate               Acid                  hypophosphite                         pH                           ture (°C.)                                (A/dm.sup.2)                                    (A/dm.sup.2)                                        T.sub.ON /T.sub.C                                            (msec)     __________________________________________________________________________     Example 1           400 1.5                  0      6.5                           50   20  4   0.2 2     Example 2           400 1.5                  0.8    6.3                           50   20  4   0.2 2     Example 3           400 1.5                  0.8    6.5                           50   20  4   0.2 2     __________________________________________________________________________

Table 32 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the content S (which indicates the amount present) of oriented Fe crystals, the O content, the P content, the B content and the hardness of a section of the slide surface construction for the examples 1 to 3.

                                      TABLE 32     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals                 O   P   B     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            content                                                content                                                    content                                                        Hard-     surface           slide                rate A                    size                        crystals            (% by                                                (% by                                                    (% by                                                        ness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                weight)                                                    weight)                                                        HmV     __________________________________________________________________________     Example 1           Hexagonal                90  0.5-2                        0.9 1.8 5.1 1.8 90.4                                            0.2 very                                                    0.01                                                        420           pyramid-                             small           shaped     Example 2           Hexagonal                90  0.5-3                        2.5 0.3 4.8 1.5 90.9                                            very                                                0.04                                                    0.01                                                        445           pyramid-                         small           shaped     Example 3           Hexagonal                90  0.5-3                        2.3 0.4 4.6 1.4 91.3                                            0.2 0.04                                                    0.01                                                        470           pyramid-           shaped     __________________________________________________________________________

The area rate A, the grain size and the content S were determined in the same manner as in section (Ia) above. The O content was determined in the same manner as in section (Ia), and the P content was determined in the same manner as in section (Ib). The measurement of the B content was carried out by a procedure which comprises peeling-off each of the examples 1 to 3 from the substrate 2 and then subjecting each example to an analysis according to a curcumin absorptiometry (JIS G1227). The term "very small" for the O content in Table 32 indicates, for example, about 0.02% by weight, and the term "very small" for the P content in Table 32 indicates, for example, about 0.01% by weight.

FIG. 24 is a photomicrograph showing the crystal structure of a vertical section of the example 1, wherein a large number of columnar Fe crystals are observed. FIG. 25 shows results provided by an analysis carried out according to an Auger electron spectrometry (AES). The analysis was carried out by sampling one columnar Fe crystal from the example, and applying fast electron beams to a side of the columnar Fe crystal to measure a concentration of B in a depthwise direction. It can be seen from FIG. 25 that the concentration of B is higher in the side of the columnar Fe crystal and therefore, boron (B) was preferentially precipitated at a grain boundary between the columnar Fe crystals.

As is apparent from the comparison of the example 1 in Table 32 with the example 3 in Table 6, the example 2 in Table 32 with the example 3 in Table 15, and the example 3 in Table 32 with the example 1 in Table 21, if the B content is set in a range of B≧0.01% by weight when O content≧0.2% by weight and/or P content≧0.04% by weight, the grain size of the columnar Fe crystals is decreased, and the hardness is increased more than that of the slide surface construction which does not contain boron (B).

Further, the example 1 in Table 32 and the example 3 in Table 6 having the same O content were subjected to a tensile test which will be described below. The examples 1 and 3 were peeled off from the substrates, and a tension load was applied to the examples 1 and 3 in a direction intersecting a direction of growth of the columnar Fe crystals. A test piece had a length in such intersecting direction of 50 mm, a width of 40 mm and a thickness of 20 μm.

As a result, it was made clear that the example 1 in Table 32 had a tensile strength of 410 MPa, while the example 3 in Table 6 had a tensile strength of 275 MPa, and that the increase in strength of the example 1 in Table 32 was achieved by the precipitation of boron (B) at the grain boundary.

Then, chips of the examples 1 to 3 were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 33. Conditions for the seizure test were identical to those described in section (Ia).

                  TABLE 33     ______________________________________     Slide surface construction                     Seizure generating load (N)     ______________________________________     Example 1       2100     Example 2       2200     Example 3       2550     ______________________________________

FIG. 26 is a graph illustrating the relationship between the contained elements and the seizure generating load for the examples 1 to 3. As is apparent from Table 33 and FIG. 26, the seizure generating load for the examples 1 to 3 is largely increased with an increase in hardness, as described above, as compared with the example 3 in Table 10, the example 3 in Table 19 and the example 1 in section (Ic), respectively. In addition, the example 2 containing phosphorus (P) and boron (B) has a seizure resistance superior to the example 1 containing oxygen (O) and boron (B), and the seizure generating load for the example 3 containing oxygen (O), phosphorus (P) and boron (B) is the highest.

Of course, it is required that the area rate A of the hexagonal pyramid-shaped Fe crystals in the slide surface is in a range of A≧40% even with the slide surface construction containing at least one of oxygen (O) and phosphorus (P), and boron (B), as described above.

Fourth Embodiment

The fourth embodiment will be described as for a slide surface construction, which is formed of an aggregate of Fe crystals. In this slide surface construction, the aggregate has a large number of columnar Fe crystals which are grown from a substrate and whose tip ends are formed of hexagonal pyramid-shaped Fe crystals, and the hexagonal pyramid-shaped Fe crystals exist in the slide surface. Further, the aggregate contains at least one of oxygen (O) and phosphorus (P), boron (B) and at least one of hydrogen (H) and carbon (C).

(IVa) Slide surface construction containing oxygen (O), boron (B), and at least one of hydrogen (H) and carbon (C)

A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of a pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 20 μm.

Table 34 shows conditions for the electrolytic Fe-plating process for examples 1 to 3 of the slide surface constructions. The plating time was varied within a range of 10 to 60 minutes in order to set the thickness of the examples 1 to 3 at 20 μm, as described above. The amount of liquid replenisher supplied was set at 0.5 liters/min.

                                      TABLE 25     __________________________________________________________________________               Plating bath     Slide Composition (g/liter)                               Pulse current process     surface           Ferrous               Boric     Temperature                               CDmax                                   CDm     T.sub.ON     construction           sulfate               Acid                  Saccharine                       pH                         (°C.)                               (A/dm.sup.2)                                   (A/dm.sup.2)                                       T.sub.ON /T.sub.C                                           (msec)     __________________________________________________________________________     Example 1           400 1.5                  0    6.5                         45    20  4   0.2 2     Example 2           400 1.5                  0.75 6.5                         50    40  8   0.2 2     Example 3           400 1.5                  0.75 6.5                         45    40  8   0.2 2     __________________________________________________________________________

Table 35 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the content (amount present) S of the oriented Fe crystals, the O content, the B content, the H content, the C content, and the hardness of the section of the slide surface construction for the examples 1 to 3 of the slide surface constructions.

                                      TABLE 35     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented                                            O content                                                 B content                                                      H content                                                           C                                                                Hard-nt     surface           slide                rate A                    size                        Fe crystals         (% by                                                 (% by                                                      (% by                                                           (%                                                                ness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 weight)                                                      weight)                                                           weight)                                                                HmV     __________________________________________________________________________     Example 1           Hexagonal                90  0.5-2                        0.8 0.7 5.3 2.5 90.7                                            0.2  0.01 0.01 very 450           pyramid-                                        small           shaped     Example 2           Hexagonal                90  0.5-2                        0.6 1.4 5.1 1.7 91.2                                            0.2  0.01 very 0.03 460           pyramid-                                   small           shaped     Example 3           Hexagonal                90  0.5-1                        1   1.7 4.8 2.5 90  0.2  0.01 0.01 0.03 480           pyramid-           shaped     __________________________________________________________________________

The area rate A, the grain size and the content S were determined in the same manner as in section (Ia) above. The O content was determined in the same manner as in section (Ia); the H and C contents were determined in the same manner as in section (IIa), and the B content was determined in the same manner as in the third embodiment.

As is apparent from the comparison of the examples 1 to 3 in Table 35 with the example 1 in Table 32, if the H content and/or the C content are set in ranges of H≧0.01% by weight and C≧0.03% by weight when O≧0.2% by weight and B≧0.01% by weight, the hardness is increased more than that of the slide surface construction which does not contain hydrogen (H) and/or carbon (C).

Then, chips of the examples 1 to 3 were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 36. Conditions for the seizure test are identical to those described in section (Ia).

                  TABLE 36     ______________________________________     Slide surface construction                     Seizure generating load (N)     ______________________________________     Example 1       2300     Example 2       2450     Example 3       2600     ______________________________________

FIG. 27 is a graph illustrating the relationship between the contained elements and the seizure generating load for the examples 1 to 3. As is apparent from Table 36 and FIG. 27, the seizure generating load for the examples 1 to 3 is largely increased with an increase in hardness, as described above, as compared with the example 1 in Table 33. In addition, the example 2 containing oxygen (O), boron (B) and carbon (C) has a seizure resistance superior to the example 1 containing oxygen (O), boron (B) and hydrogen (H), and the seizure generating load for the example 3 containing oxygen (O), boron (B), hydrogen (H) and carbon (C) is the highest.

Of course, it is required that the area rate A of the hexagonal pyramid-shaped Fe crystals in the slide surface is in a range of A≧40% even with the slide surface construction containing oxygen (O), boron (B), and at least one of hydrogen (H) and carbon (C), as described above.

(IVb) Slide surface construction containing phosphorus (P), boron (B), and at one least hydrogen (H) and carbon (C)

A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of a pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 20 μm.

Table 37 shows conditions for the electrolytic Fe-plating process for examples 1 to 3 of the slide surface constructions 4. The plating time was varied within a range of 10 to 60 minutes in order to set the thickness of the examples 1 to 3 at 20 μm, as described above. The amount of liquid replenisher supplied was set at 0.5 liters/min.

                                      TABLE 37     __________________________________________________________________________     Plating bath     Slide Composition (g/liter)      Pulse current process     surface           Ferrous               Sodium hypo-                           Boric                                Temperature                                      CDmax                                          CDm     T.sub.ON     construction           sulfate               phosphite                      Saccharine                           Acid                              pH                                (°C.)                                      (A/dm.sup.2)                                          (A/dm.sup.2)                                              T.sub.ON /T.sub.C                                                  (msec)     __________________________________________________________________________     Example 1           400 0.8    0    1.5                              6.3                                48    20  4   0.2 2     Example 2           400 0.5    0.75 1.5                              6.3                                50    40  8   0.2 2     Example 3           400 0.5    0.75 1.5                              6.3                                48    40  8   0.2 2     __________________________________________________________________________

Table 38 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the content (amount present) S of the oriented Fe crystals, the P content, the B content, the H content, the C content, and the hardness of the section of the slide surface construction for the examples 1 to 3 of the slide surface constructions.

                                      TABLE 38     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals     Slide form of                Area                    Grain                        Content S (%) of oriented                                            P content                                                 B content                                                      H content                                                           C                                                                Hard-nt     surface           slide                rate A                    size                        Fe crystals         (% by                                                 (% by                                                      (% by                                                           (%                                                                ness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                 weight)                                                      weight)                                                           weight)                                                                HmV     __________________________________________________________________________     Example 1           Hexagonal                90  0.5-3                        3   0.3 4.5 1.8 90.4                                            0.04 0.01 0.01 very 455           pyramid-                                        small           shaped     Example 2           Hexagonal                90  0.5-3                        2.8 0.4 4.7 1.9 90.2                                            0.04 0.01 very 0.03 465           pyramid-                                   small           shaped     Example 3           Hexagonal                90  0.5-3                        2.5 0.5 5   1.7 90.3                                            0.04 0.01 0.01 0.03 485           pyramid-           shaped     __________________________________________________________________________

The area rate A, the grain size and the content S were determined in the same manner as in section (Ia) above. The P content A was determined in the same manner as in section (Ib); the H and C contents were determined in the same manner as in section (IIa), and the B content was determined in the same manner as in the third embodiment.

As is apparent from the comparison of the examples 1 to 3 in Table 38 with the example 2 in Table 32, if the H content and/or the C content are set in ranges of H≧0.01% by weight and C≧0.03% by weight when P≧0.04% by weight and B≧0.01% by weight, the hardness is increased more than that of the slide surface construction which does not contain hydrogen (H) and/or carbon (C).

Then, chips of the examples 1 to 3 were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 39. Conditions for the seizure test are identical to those described in section (Ia).

                  TABLE 39     ______________________________________     Slide surface construction                     Seizure generating load (N)     ______________________________________     Example 1       2300     Example 2       2450     Example 3       2600     ______________________________________

FIG. 28 is a graph illustrating the relationship between the contained elements and the seizure generating load for the examples 1 to 3. As apparent from Table 39 and FIG. 28, the seizure generating load for the examples 1 to 3 is largely increased with an increase in hardness, as described above, as compared with the example 1 in Table 33. In addition, the example 2 containing phosphorus (P), boron (B) and carbon (C) has a seizure resistance superior to the example 1 containing phosphorus (2), boron (B) and hydrogen (H), and the seizure generating load for the example 3 containing phosphorus (P), boron (B), hydrogen (H) and carbon (C) is the highest.

Of course, it is required that the area rate A of the hexagonal pyramid-shaped Fe crystals in the slide surface is in a range of A≧40% even with the slide surface construction containing phosphorus (P), boron (B), and at least one of hydrogen (H) and carbon (C), as described above.

(IVc) Slide surface construction containing oxygen (O), phosphorus (P), boron (B), and at least one of hydrogen (H) and carbon (C).

A plurality of piston pins 1 for an internal combustion engine were produced by subjecting an outer peripheral surface 3 of a pipe-like substrate 2 made of a steel (JIS SCM420) to an electrolytic Fe-plating process to form a slide surface construction 4 formed of an aggregate of Fe crystals and having a thickness of 20 μm.

Table 40 shows conditions for the electrolytic Fe-plating process for examples 1 to 3 of the slide surface constructions 4. The plating time was varied within a range of 10 to 60 minutes in order to set the thickness of the examples 1 to 3 at 20 μm, as described above. The amount of liquid replenisher supplied was set at 0.5 liters/min.

                                      TABLE 40     __________________________________________________________________________     Plating bath     Slide Composition (g/liter)      Pulse current process     surface           Ferrous               Sodium hypo-                           Boric                                Temperature                                      CDmax                                          CDm     T.sub.ON     construction           sulfate               phosphite                      Saccharine                           Acid                              pH                                (°C.)                                      (A/dm.sup.2)                                          (A/dm.sup.2)                                              T.sub.ON /T.sub.C                                                  (msec)     __________________________________________________________________________     Example 1           400 0.8    0    1.5                              6.5                                45    20  4   0.2 2     Example 2           400 0.5    0.75 1.5                              6.5                                50    40  8   0.2 2     Example 3           400 0.5    0.75 1.5                              6.5                                45    40  8   0.2 2     __________________________________________________________________________

Table 41 shows the crystal form of the slide surface, the area rate A and grain size of the hexagonal pyramid-shaped Fe crystals in the slide surface, the content (amount present) S of the oriented Fe crystals, the O content, the P content, the B content, the H content, the C content and the hardness of the section of the slide surface construction for the examples 1 to 3 of the slide surface constructions.

                                      TABLE 41     __________________________________________________________________________                Hexagonal                pyramid-shaped     Crystal    Fe crystals                 O   P   B   H   C     Slide form of                Area                    Grain                        Content S (%) of oriented Fe                                            content                                                content                                                    content                                                        content                                                            content                                                                Hard-     surface           slide                rate A                    size                        crystals            (% by                                                (% by                                                    (% by                                                        (% by                                                            (%                                                                ness     construction           surface                (%) (μm)                        {110}                            {200}                                {211}                                    {310}                                        {222}                                            weight)                                                weight)                                                    weight)                                                        weight)                                                            weight)                                                                HmV     __________________________________________________________________________     Example 1           Hexagonal                90  0.5-3                        2.5 0.5 4.5 1.5 91  0.2 0.04                                                    0.01                                                        0.01                                                            very                                                                490           pyramid-                                         small           shaped     Example 2           Hexagonal                90  0.5-2                        2.3 0.5 5.1 1.9 90.2                                            0.2 0.04                                                    0.01                                                        very                                                            0.03                                                                500           pyramid-                                     small           shaped     Example 3           Hexagonal                90  0.5-2                        2.3 0.7 5   2   90  0.2 0.04                                                    0.01                                                        0.01                                                            0.03                                                                520           pyramid-           shaped     __________________________________________________________________________

The area rate A, the grain size and the content S were determined in the same manner as in section (Ia). The O content was determined in the same manner as in section (Ia); the P content was determined in the same manner as in section (Ib); the H and C contents were determined in the same manner as in section (IIa), and the B content was determined in the same manner as in the third embodiment.

As is apparent from the comparison of the examples 1 to 3 in Table 41 with the example 3 in Table 32, if the H content and/or the C content are set in ranges of H≧0.01% by weight and C≧0.03% by weight when O≧0.2% by weight; P≧0.04% by weight and B≧0.01% by weight, the hardness is increased more than that of the slide surface construction which does not contain hydrogen (H) and/or carbon (C).

Then, chips of the examples 1 to 3 were fabricated and subjected to a seizure test in a chip-on-disk manner under lubrication to measure the seizure generating load, thereby providing the results given in Table 42. Conditions for the seizure test are identical to those described in section (Ia).

                  TABLE 42     ______________________________________     Slide surface construction                     Seizure generating load (N)     ______________________________________     Example 1       2700     Example 2       2850     Example 3       3000     ______________________________________

FIG. 29 is a graph illustrating the relationship between the contained elements and the seizure generating load for the 

What is claimed is:
 1. A slide surface construction, which is formed of an aggregate of metal crystals, wherein the area rate A of pyramid-shaped metal crystals in the slide surface is in a range of A≧40%, and said aggregate contains phosphorous (P) in a content greater than or equal to 0.04% by weight and, optionally, oxygen (O) in a content greater than or equal to 0.2% by weight.
 2. A slide surface construction, which is formed on an aggregate of metal crystals, wherein the area rate A of pyramid-shaped metal crystals in the slide surface is in a range of A≧40%, and said aggregate contains phosphorous (P), at least one of hydrogen (H) and carbon (C ), and, optionally, oxygen (O), the O content being greater than or equal to 0.2% by weight, the P content being greater than or equal to 0.04% by weight, the H content being greater than or equal to 0.01% by weight, and the C content being greater than or equal to 0.03% by weight.
 3. A slide surface construction, which is formed of an aggregate of metal crystals, wherein said aggregate includes a large number of columnar metal crystals which are grown from a substrate and whose tip ends are formed of pyramid-shaped metal crystals, the area rate A of said pyramid-shaped metal crystals in the slide surface being in a range of A≧40%, and said aggregate contains boron (B), phosphorous (P) and optionally, oxygen (O), the B content being greater than or equal to 0.01% by weight, the O content being greater than or equal to 0.2% by weight, and the P content being greater than or equal to 0.04% by weight.
 4. A slide surface construction, which is formed of an aggregate of metal crystals, wherein said aggregate includes a large number of columnar metal crystals which are grown from a substrate and whose tip ends are formed of pyramid-shaped metal crystals, the area rate A of said pyramid-shaped metal crystals in the slide surface being in a range of A≧40%, and said aggregate contains boron (B), phosphorous (P), at least one of hydrogen (H) and carbon (C), and, optionally, oxygen (O), the B content being greater than or equal to 0.01% by weight, the O content being greater than or equal to 0.01% by weight, and the C content being greater than or equal to 0.03% by weight.
 5. A slide surface construction according to claim 1, 2, 3 or 4, wherein each said metal crystal has a body-centered cubic structure, and each said pyramid-shaped metal crystal is either an (hhh) oriented metal crystal with its (hhh) planes by Miller indices oriented toward the slide surface or a (2hhh) oriented metal crystal with its (2hhh) planes by Miller indices oriented toward the slide surface.
 6. A slide surface construction according to claim 1, 2, 3, or 4, wherein each said metal crystal is an Fe crystal, and each said pyramid-shaped metal crystal is a hexagonal pyramid-shaped (hhh) oriented Fe crystal with its (hhh) planes by Miller indices oriented toward the slide surface.
 7. A slide surface construction according to claim 5, wherein each said metal crystal is an Fe crystal, and each said pyramid-shaped metal crystal is a hexagonal pyramid-shaped (hhh) oriented Fe crystal with its (hhh) planes by Miller indices oriented toward the slide surface.
 8. A slide surface construction, which is formed of an aggregate of metal crystals, wherein the area rate A of pyramid-shaped metal crystals in the slide surface is in a range of A≧40%, and said aggregate contains phosphorous (P), at least one of boron (B), hydrogen (H) and carbon (C), and, optionally, oxygen (O), the O content being greater than or equal to 0.2% by weight, the P content being greater than or equal to 0.04% by weight, the B content being greater than or equal to 0.01% by weight, the H content being greater than or equal to 0.01% by weight, and the C content being greater than or equal to 0.03% by weight.
 9. A slide surface construction according to claim 8, wherein each said metal crystal has a body-centered cubic structure, and each said pyramid-shaped metal crystal is either an (hhh) oriented metal crystal with its (hhh) planes by Miller indices oriented toward the slide surface or a (2hhh) oriented metal crystal with its (2hhh) planes by Miller indices oriented toward the slide surface.
 10. A slide surface construction according to claim 8, wherein each said metal crystals is an Fe crystal, and each said pyramid-shaped metal crystal is a hexagonal pyramid-shaped (hhh) oriented Fe crystal with its (hhh) planes by Miller indices oriented toward the slide surface.
 11. A slide surface construction, which is formed of an aggregate of metal crystals, wherein the area rate A of pyramid-shaped metal crystals in the slide surface is in a range of A≧40%, and said aggregate contains oxygen (O), phosphorous (P), boron (B), hydrogen (H) and carbon (C), the O content being greater than or equal to 0.2% by weight, the P content being greater than or equal to 0.04% by weight, the B content being greater than or equal to 0.01% by weight, the H content being greater than or equal to 0.01% by weight, and the C content being greater than or equal to 0.03% by weight.
 12. A slide surface construction according to claim 1, 2, 3, 4 or 8, wherein the O content is ≧22.9% by weight.
 13. A slide surface construction according to claim 1, 2, 3, 4 or 8, wherein the P content is ≧11.5% by weight.
 14. A slide surface construction according to claim 2, 4 or 8, wherein the H content is ≧0.1% by weight.
 15. A slide surface construction according to claim 2, 4 or 8, wherein the C content is ≧0.8% by weight.
 16. A slide surface construction according to claim 3, 4 or 8, wherein the B content is ≧3.7% by weight.
 17. A slide surface construction according to claim 8 or 11, wherein the O content is ≧22.9% by weight, the P content is ≧11.5% by weight, the H content is ≧0.1% by weight, the C content is ≧0.8% by weight, and the B content is ≧3.7% by weight. 